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Full text of "SAE J839B: Passenger Car Side Door Latch System"

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By Authority Of 

THE UNITED STATES OF AMERICA 

Legally Binding Document 



By the Authority Vested By Part 5 of the United States Code § 552(a) and 
Part 1 of the Code of Regulations § 51 the attached document has been duly 
INCORPORATED BY REFERENCE and shall be considered legally 
binding upon all citizens and residents of the United States of America. 
HEED THIS NOTICE : Criminal penalties may apply for noncompliance. 




Document Name: SAE J839B: Passenger Car Side Door Latch System 



CFR Section(s): 49 CFR 571.201 



Standards Body: Society of Automotive Engineers 



SAFETY GLAZING MATERIALS 



999 




PASSENGER CAR 

SIDE DOOR LATCH SYSTEMS — SAE J839b 



SAE Recommended Practice 



Report of Body Engineering Committee approved November 1962 and last revised May 1965. Editorial change January 1968. 



1. Scope— This SAE Recommended Practice establishes minimum per- 
formance requirements and test procedures for evaluating and testing 
passenger car side door latch systems. It is limited to tests that 
can be conducted on uniform test fixtures and equipment in commer- 
cially available laboratory test facilities. 

The test procedures and minimum performance requirements out- 
lined in this recommended practice are based on currently available en- 
gineering data. It is intended that all portions of the recommended 
practice will be periodically reviewed and revised, as additional knowl- 
edge regarding vehicle latch performance under impact conditions is 
developed. 

2. Terminology 

2.1 Latch— A mechanical device employed to position the door in 
a closed position relative to the vehicle body with provisions for con- 
trolled release (or operation) . 



Basic Latch Components (Nomenclature) are: 

Plate— The main body or frame for supporting working components, 
appendages and transmitting or distributing loads to the door structure. 

Rotor (or Bolt) —The rotating or sliding member of the latch which 
engages and restrains the latch to the striker. 

Ratchet— A member of the latch connected to the rotor to provide an 
abutment or abutments which, when properly indexed, become engaged 
with a related pawl to inhibit motion of the rotor in one direction. 

Pawl— A member of the latch that can be caused to engage the abut- 
ments of the ratchet to inhibit relative motion between the two parts 
except in one direction. 

2.2 Striker— A mechanical device with which the latch engages on 
the opposing member of the body. 

2.3 Fully Latched Position— The attitude that exists between the 
latch and striker when the door is securely positioned in the fully 



1000 



PASSENGER CAR SIDE DOOR LATCH SYSTEMS 



ADAPT THE TEST FIXTURE TO THE 
MOUNTING PROVISIONS OF THE 
LATCH AND STRIKER 




EQUALIZING LINKS 



INTERCHANGEABLE LATCH MOUNTING 
PLATE (RECOMMENDED GAGE. 121.010) 



INTERCHANGEABLE STRIKER MOUNTING PLATE 
(RECOMMENDED GAGE .12 ♦. 010) 



FIG. 1-DOOR LATCH-STATIC LOAD TEST FIXTURE (LONGITUDINAL LOAD) 



closed position. 

2.4 Secondary Latched Position— The attitude that exists between 
the latch and striker when the latch holds the door in a position less 
than fully closed. 

NOTE: The secondary latched position may be included in the side 
door latch, as an added mechanical feature to reduce the possibility of 
the door opening freely, in the event the door is not closed to the fully 
latched position. It should be recognized that doors are intended to be 
in the fully latched position whenever the vehicle is in motion. 

5. Basic Requirements 

3.1 Longitudinal Load— An automotive door latch and striker as- 
sembly, when tested as described under test procedures, must be able 
to withstand an ultimate longitudinal load of 2500 lb when in the full} 
latched position (see paragraph 4.1) and 1000 lb when in the secondary 
latched position (see paragraph 4.2). 

3.2 Transverse Load— An automotive door latch and striker assem- 
bly, When tested as described under test procedures, must be able to 
withstand an ultimate transverse load of 2000 lb When in the fully 
latched position (see paragraph 4.3) and 1000 lb when in the secondary 
latched position (see paragraph 4.4). 

3.3 Inertia Load— An automotive door latch, when contained in 
the door latch system (including the door latch, striker assembly, out- 
side handle, key cylinder and any connecting mechanisms) and, in the 
fully latched position, when evaluated by calculation, must remain in 
the fully latched position when subjected to an inertia load of 30 g in 
any direction. (See paragraph 5.) 

NOTE: Due to the interdependency of the components, it is im- 
portant that the door latch be analyzed within the confines of the total 
system and these results considered the basis of acceptance. 

4. Static Tests 
4.1 Longitudinal Load— Fully Latched Position— 

4.1.1 Purpose— To determine the ability of the vehicle latch and 
striker to withstand a test load perpendicular to the face of the latch. 

4.1.2 Equipment— 

(a) Tensile testing machine. 

(b) Static test fixture (see Fig. 1). 



4.1.3 Operation— 

(a) Attach the test fixture to the mounting provisions of the latch 
and striker. Align the direction of engagement parallel to the linkage 
of the fixture. Mount fixture with latch and striker in fully latched 
position in the test machine so as to apply a load perpendicular to the 
face of the latch. 



it 



ADAPT THE TEST FIXTURE 

TO THE MOUNTING PROVISIONS £% 

OF THE LATCH AND STRIKER. 



APPLIED LOAD SIMULATING 
LATERAL OUTBOARD DOOR 
OPENING. u PULL' TO BE IN 
LINE WITH CONTACTING SUR- 
FACES OF THE LATCH AND 
STRIKER." 




FIG. 2-DOOR LATCH-STATIC LOAD FIXTURE (LATERAL 

LOAD) 



PASSENGER CAR SIDE DOOR LATCH SYSTEMS 



1001 



(b) Locate weights to apply a 200 lb load tending to separate the 
latch and striker in the direction of the door opening. 

(c) Apply the test load at a rate not to exceed 0,2 in. per minute 
until failure. .Record maximum load. 

4.2 Longitudinal Load— Secondary Latched Position— 

4.2.1 Purpose— To determine the ability of the vehicle latch and 
striker in the secondary position to withstand a test load perpendicular 
to the face of the latch. 

4.2.2 Equipment— 

(a) Tensile testing machine. 

(b) Static test fixture (see Fig. 1). 

4.2.3 Operation— 

(a) Attach the test fixture to the mounting provisions of the latch- 
and striker. Align the direction of engagement parallel to the linkage 
of the fixture. Mount fixture with latch and striker in secondary latched 
position in the test machine as so to apply a load perpendicular to the 
face of the latch. 

(b) Locate weights to apply to 200 lb load tending to separate the 
latch and striker in the direction of the door opening. 

(c) Apply the test load at a rate not to exceed 0.2 in. per minute 
until failure. Record maximum load. 

4.3 Transverse Load— Fully Latched Position— 

4:3.1 Purpose— To determine the ability of the vehicle latch and 
striker to withstand the test load in the direction of door opening. 

4.3.2 Equipment— 

(a) Tensile testing machine. 

(b) Static test fixture (see Fig. 2). 

4.3.3 Operation— 

. (a) Adapt the test fixture to the mounting provisions of the latch 
and striker. Mount, fixture with the latch and striker in fully latched 
position in the test machine so as to apply a load in the dir^tion oi 
door opening. 

(b) Apply the test load at a rate not to exceed 0.2 in. per minute 
until failure. Record the maximum load. 



4:4 Transverse Load— Secondary Latched Position— 

4.4.1 Purpose— To determine the ability of the vehicle latch and 
striker in the secondary position to withstand the test load in the direc- 
tion of door opening. 

4.4.2 Equipment— 

(a) Tensile testing machine. 

(b) Static test fixture (see Fig. 2). 

4.4.3 Operation— . 

(a) Adapt the test fixture to the mounting provisions of the latch 
and striker. Mount fixture with the latch and striker in secondary 
latched position in the test machine so as to apply a load in the direc- 
tion of door opening. 

(b) Apply the test load at a rate not to exceed 0.2 in. per minute 
until failure. Record the maximum load. 

5. Inertial Analysis 

5.1 Purpose— To determine the ability of the vehicle latch system 
to resist inertia loading by means of a mathematical analysis of the 
component parts in their true car relationship. 

NOTE: Due to the complexity of physical testing for inertial charac- 
teristics it is judged to be more practical and more accurate to base 
evaluations on mathematical analysis. The procedure described in this 
section provides a means for analytically determining the ability of a 
door latch system to. withstand inertia loading. Spring forces are con- 
sidered average minimum. Friction effects and work to be done are not 
considered in the calculations. Gravitational pull on components may 
also be omitted if it tends to restrict unlatching. These omissions from 
the calculations are permissible because they provide additional factors 
of safety. 

5.2 Calculation Consideration— Each component or subassembly can 
be calculated for its minimum inertia load resistance in a particular 
direction. Their combined resistance, to the unlatching operation, must 
assure that the door latch system .(when properly assembled in the 
vehicle door) will remain latched when subjected to an inertia load of 
30 g in any direction. Fig. 3 is an example of the components and com- 
binations of components to be considered. 



W 2 =.05 LB 
d|«1.24-r F, 



d 6 =.075 




-30 g DECELERATION 

GIVEN'. 

DOOR LATCH SYSTEM SUBJECTED TO 30 g DECELERATION 

w w 

F=M a = |-a = ^30g=30W 

50 -AVE 
F 2 =W 2 X 30 = .050 LB X 30= 1.50 LB 



W 



.027 LB 



X 30 = .405 LB 



F 3 =-| 3 X30-- 2 

2M *F, Xd,-J-F 2 Xd 2 -F 3 Xd 3 =.08 LB X 1.24 IN.-t- 1.50 LB X .42IN.-.405 LB X.I9IN.= .652 IN.-LB 

F 5"d4"T24 "' 526LB 

F 6 = W 4 X 30= .093 X 30 = 2.79 LB 

2M P =PAWL SPRING OUTPUT- (F 5 d 5 +F 6 d 6 ) = 3.96 IN.-LB - (.526 X 1.48 4- 2.79 X. 075) =2.972 IN.-LB 



• DENOTES CG OF COMPONENT 



FIG. 3-INERTIA LOADING-SAMPLE CALCULATION